Understand the parameters of the axis of pandas

# How axis parameters pandas understanding? 
#     Axis = 0 or "index": 
#        If the operation is one-way, refers to a line 
#        If the polymerization operation, referring to the cross rows interbank

#     Axis = 1 or "the Columns" 
#        If a separate operation, it refers to a column 
#        if it is aggregation operations, referring to the inter-row Cross the Columns 
# according to which axis, is this axis to move, the other axis remains move



import pandas as pd 
import numpy as np

df = pd.DataFrame(
    np.arange(12).reshape(3,4),
    columns = ["A","B","C","D"]
)



#   1 single drop, is to delete a column 
df.drop ( " A " , Axis = 1 )

# 2 single-line drop, promptly remove a row 
df.drop (. 1, Axis = 0)

# 3 according to axis = 0 / index mean polymerization operation performed 
# counter-intuitive: the result is not outputted per row, but the result of each column

# axis=0 or axis = index
df.mean(axis=0)

#   4 press axis = 1 / columns mean polymerization operation performed 

df.mean (Axis =. 1 )

#    In the example, a deeper understanding 
DEF get_sum_value (X):
     return X [ " A " ] + X [ " B " ] + X [ " C " ] + X [ " D " ]
df["sum_value"] = df.apply(get_sum_value,axis=1)
df

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